Christmas markets have a long tradition here in Germany. The best known Christmas market is probably the “Christkindl’s Markt” in Nürnberg, Bavaria.
A Christmas market is not simply a modification of a regular farmers market. Other than a farmers market it opens at about 10 or 11 a.m. instead of 7 a.m. and instead of closing a noon, it stays open until about 8 p.m.
You can buy spices, fruits (during my childhood the Christmas market was the only source for buying oranges, mandarins and some other exotic fruits for the South). You can also buy candles and decoration stuff, but also some food to make you warm from the inside again or some alcoholic drinks like hot spices wine.
While the markets exist in the bigger cities from about mid November until December 23rd, they are set up only for the weekends in smaller cities. Sometimes even for only one day or one weekend. Even some farms set up Christmas markets. Often these farms grow Christmas trees and thus combine the Christmas tree sale with a small Christmas market to attract additional customers.
Have a great Advent time!